Bearings of the type described can be constructed so as to minimize or eliminate the loss of lubricant from the system and hence avoid a lack of lubrication, so that the bearing does not require maintenance during a very long operating time. Such bearings are wear-resistant and reliable, because they are lubricated sufficiently throughout their entire life. An additional advantage is that the lubricant is largely distributed in a manner which can be calculated in advance and is independent of acceleration, thereby leaving the center of mass of the shaft and the housing in its original position. Because the lubricant flows through the porous lubricant reservoir in its recirculation, the lubricant is continually filtered, so that no contamination which might cause wear reaches the bearing area. The lubricant reservoir can be made coaxial with the bearing.
A known bearing of this type (German Patent Disclosure Document DE-OS 26 09 736) has a wick serving as the device which carries the lubricant from the reservoir to the bearing surface. The wick can, if suitable, be formed by the reservoir itself, and touches the surface rotating with the shaft, thereby constantly brushing lubricant onto the surface. However, every wick contains dust and, in some cases, still other types of contamination. Further contamination develops due to the abrasion to which the wick is subjected by the surface which it brushes.
Even when the friction between the wick and the surface which it contacts is very slight, and the wick is hence subjected only to slight wear, the life time of the bearing is limited by wear of the wick.